METHODOLOGY CORE PROJECT SUMMARY Methods to assess the societal and health economic impact of substance use disorder (SUD), hepatitis C (HCV), and HIV treatment need to reflect our rapidly changing healthcare system. Greater availability of health insurance through the Affordable Care Act, as well as parity requirements for SUD and mental health, are increasing access to health insurance coverage for substance users and encouraging new organizational models such as integrated healthcare systems. Conducting economic evaluations of treatments for substance users in this new context requires using both cost-benefit analysis (CBA) and cost-effectiveness analysis (CEA) methods. While CBA and CEA are most often conducted separately by researchers trained in different disciplines, our Core will bring these approaches together to maximize efficiency of data collection and depth of analyses. In addition, we will bring attention to affordability issues that are frequently raised by decision makers, using budget impact analysis methods. The overall aim of CHERISH (Center for Health Economics of TReatment Interventions for Substance Use Disorder, HCV, and HIV) is to develop and disseminate economic evidence that informs substance use treatment policy and HCV and HIV care of substance users, and to increase the impact of this research by addressing the needs of integrated healthcare system decision makers. In support of this aim, the CHERISH Methodology Core will uniquely combine expertise in CBA, CEA, and budget impact analysis methods, extensive experience conducting economic evaluations of SUD, HCV, and HIV treatment of substance users, and expertise in related fields such as advanced statistical analysis, organizational research, and clinical program evaluation. The Methodology Core?s specific aims are 1) to promote the development and application of economic evaluation methods to SUD treatment and HCV and HIV care of substance users, emphasizing the integrated healthcare system perspective, and 2) to promote harmonization of clinical and economic data collection tools and conduct health economic research to validate/modify tools that address the economic consequences of SUD, HCV, and HIV treatment. We will establish expert teams to work with research projects to extend their economic analyses and ensure their relevance to integrated healthcare system decision makers. We will establish a consultation service to assist researchers in integrating economic evaluation into planning for clinical trials or observational studies. We will work with SUD, HCV, and HIV researchers to establish common definitions of relevant economic outcomes and conduct comparative analyses of how effectively data collection tools and methods measure these outcomes. We will work with the HCV and HIV Core to ensure that their longitudinal data can be analyzed using advanced methods, with the Dissemination and Policy Core to translate economic evaluation methods for decision makers and to disseminate and promote data harmonization, and with the Pilot Grant and Training Core to evaluate and mentor pilot projects and conduct methodology training and mentoring programs.